The present invention relates to a method for producing a leaf spring as a fiber composite component for a motor vehicle as well as to a leaf spring produced with the method.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Composite materials have better mechanical properties compared to the combined components themselves. The interactions that occur when the at least two major components are joined allow an almost perfect uptake of the internal forces produced when a load is applied to component made from a composite material. In particular fiber composite materials have an advantageously high strength per weight and the components produced therefrom have high stiffness.
Starting materials are artificial or natural fibers which are processed either individually or as a fiber bundle (roving) as well as a two-dimensional textile structure. Components which can be almost universally applied and which are able to withstand high loads can be produced in combination with a matrix made of a hardening resin surrounding the individual fibers. The conventional manufacturing processes are based on using fibers impregnated with a resin, wherein the fibers are combined in a mold tool into a fiber composite component by applying pressure and heat.
Conventionally, the individual fibers in form of a fiber strand are first wetted with a not yet set plastic matrix, which penetrates and hence infiltrates the fiber strand when exposed to heat. The premature reaction of the resin is prevented by subsequent cooling, whereafter the infiltrated fiber strand is cut to length into individual prepregs. The individual prepegs are layered on top of one another in a shaping mold tool and hardened by applying pressure and heat. The finished leaf spring is produced in a subsequent finishing step.
The necessary measures for infiltrating and cooling the fiber strand are complex. In particular, cooling must be maintained until shortly before the prepegs are used so as to retain the binding properties of the resin. In addition, the prepegs with the not yet set resin are difficult to handle. Layering the sticky prepegs also requires a high degree of precision in order to ensure that the prepegs are as congruent as possible and have few air inclusions.
In particular, layering therefore requires an increased expenditure of time. Moreover, attention should also be paid to the end regions of the component so as to prevent notch effects or exposed ends of the fibers, which could weaken the fiber composite component and hence shorten its service life.
In view of this background, there is still room for improvements to make industrial production of springs in form of fiber composite materials more economical.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method for producing a leaf spring as a fiber composite component for a motor vehicle by simplifying handling of the fibers infiltrated with resin and making the overall production process more economical. It would also be desirable and advantageous to provide a leaf spring produced with this method, which can be manufactured with higher precision particularly in its edge and end regions in spite of the more economical manufacturing process.